Human papillomaviruses (HPVs) are classified into "types," "subtypes," and variants." HPV16 and 18 are types known to be central to the pathogenesis of most invasive cervical cancers (ICC) and their precursor lesion, cervical intraepithelial neoplasia (CIN) grade 2-3. However, many women acquire and spontaneously resolve cervical infections with these HPV types. We hypothesize that certain HPV 1 6 and 18 variants differ in their biologic behavior and risk of cervical neoplasia. A number of small studies have examined associations between HPV 1 6 and 18 variants and risk of cervical neoplasia and many, but not all, suggest differences in biologic behaviors. Confirmation of these findings in large, more representative populations is essential. We propose to efficiently examine these issues by performing additional assays on a subset of samples collected during the ongoing NCI-sponsored, multi-center randomized clinical trial: ASCUS/LSIL Triage Study (ALTS). This study, which includes 5,086 women from four different regions of the country, is examining how to best manage women referred with a cytologic diagnosis of atypical squamous cells of uncertain significance (ASCUS) or low- grade squamous intraepithelial lesions (LSIL) of the cervix. The ALTS dataset is extremely rich with results from standardized collection and testing of clinical specimens, detailed questionnaires with information on potential confounders, and histologic and colposcopic diagnoses provided by expert panel review. By including data from only those women enrolled in the immediate colposcopy arm of ALTS, we will develop precise estimates of the association between HPV 1 6 and IS variants and cervical neoplasia (aims 1 and 2), and determine whether those variants that are associated with CIN 2-3 have increased DNA levels or specific nucleotide changes in the LCR and E6 regions of the genome (aim 4). Furthermore, using data from women enrolled in the immediate colposcopy and conservative management arms, we will provide the first observations on the relationship between HPV 1 6 variants and risk for recurrence after treatment for CIN 2-3 (aim 3). To address these aims, we will perform PCR-based assays for detection and typing of 7,290 samples, classify (by DNA sequencing) HPV variants present in samples from women infected with HPV16 (n=548) or 18 (n=222), and quantify (by a PCR-based kinetic thermocycling assay) the amount of HPV DNA present in the 1,915 HPV16-positive and 222 HPV18-positive samples. The proposed study is likely to make important contributions to our understanding of the role of HPV 16 and 18 variants in the pathogenesis of cervical cancer.